In network architecture upgrades, two criteria that are often considered and traded off one against another include: a) proper sizing of “service groups” to enable enough capacity to meet eventual customers' demand (even at the later stage of life of the proposed upgrade) and b) enabling a cost-effective start (e.g., with just the right amount of capacity to serve customers demand in the early stage of life). The networks are organized into “service groups” to which a certain bandwidth capacity is assigned to, both in downstream (DS) and upstream (US) directions. For example, a service group may start at 200 users or 400 homes passed (if it is assumed only 50% of homes passed may subscribe to the service). As the bandwidth capacity is expected to grow in time, the service groups may be split into additional service groups, such as two, four, eight, etc. service groups, to meet the growing demand. For example, the service group may be split into two service groups of 100, and then four service groups of 50. However, delaying those service group splits will save the cost needed to perform the “split” until the time the additional service groups are necessary.
A network may include 16 fiber deep (FD) nodes that may each feed a number of homes, such as 20-80 homes, via a single fiber link for both the downstream and the upstream directions. To transition to this type of network, a network provider may want to develop the network in phases. An end goal may be a maximum of eight dense wavelength division multiplexing (DWDM) downstream transmitters (TXs) and a maximum of 16 coarse wavelength division multiplexing (CWDM) upstream receivers (RXs). Also, the end goal may be two FD nodes per transmitter in the downstream and one FD node per receiver in the upstream. However, the network provider may convert the network using multiple phases before reaching the end goal.
A possible phase 1 configuration may be eight FD nodes per transmitter in the downstream and four FD nodes per receiver in the upstream. A possible phase 2 configuration may include four FD nodes per transmitter in the downstream and two FD nodes per receiver in the upstream. Changing from phase 1 to phase 2, and then to the end goal (e.g., phase 3) requires both head end and field changes. For example, at the head end, when the transmitter and receiver additions are made, the multiplexer in the head end upstream path needs to be replaced at every phase-to-phase conversion, such as from a four output CWDM de-multiplexer in phase 1 to an eight output CWDM de-multiplexer in phase 2, and eventually to a 16 output CWDM de-multiplexer in phase 3. The 4-CWDM and 8-CWDM de-multiplexers may not be standard de-multiplexers and may have to be custom-manufactured, which increases the cost.
In the field, in the downstream direction, splitters will require reconfiguration at each phase conversion. For example, phase 1 may require three levels of splitters; phase 2 will require two levels of splitters; and phase 3 will require only one level of splitters. This will require that a network provider go out into the field (e.g., truck rolls) to access the splitters and reconfigure the splitters in the field. The reconfiguration may also require service outages in addition to the cost for the service provider to go into the field.